Apparatus and method for reducing papr of preamble signal in digital broadcasting system

ABSTRACT

A method and apparatus for reducing a Peak to Average Power Ratio (PAPR) in a digital broadcasting system are provided. Reserved tones are determined, and the determined reserved tones are used to transmit a signal having an impulse characteristic in locations of sub-carriers that do not collide with a pilot signal of a preamble in a frame. The signal having the impulse characteristic is transmitted through the reserved tones in a symbol interval for which the preamble is transmitted.

PRIORITY

This application claims priority under 35 U.S.C. §119(a) to a KoreanPatent Application filed in the Korean Intellectual Property Office onApr. 28, 2008 and assigned Serial No. 10-2008-0039137, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a transmission apparatus andmethod in a digital broadcasting system. More particularly, the presentinvention relates to an apparatus and method for reducing a Peak toAverage Power Ratio (PAPR) of a preamble signal in a digitalbroadcasting system.

2. Description of the Related Art

Digital broadcasting systems are broadcasting systems that use digitaltransmission technologies, such as Digital Audio Broadcasting (DAB),Digital Video Broadcasting (DVB) and Digital Multimedia Broadcasting(DMB).

Among them, the DVB system, which is a European digital broadcastingtechnology, is a transmission standard that supports existing digitalbroadcast services for fixed terminals as well as digital multimediaservices for mobile and portable terminals.

In the DVB system, it is possible to multiplex Moving Picture ExpertsGroup 2 Transport Stream (MPEG 2 TS)-based broadcast data andsimultaneously transmit Internet Protocol (IP)-based data streams.Further, in the DVB system, several services can be multiplexed to oneIP stream and transmitted. After receiving data of the transmitted IPstream, a user terminal can demultiplex the received data back intoindividual services, demodulate the services, and display thedemodulated services on a screen of the user terminal. In this case, theuser terminal requires information about various types of servicesprovided in the DVB system, the details contained in each of theservices, etc.

The DVB system uses an Orthogonal Frequency Division Multiplexing (OFDM)transmission scheme. Although the OFDM transmission scheme is similar tothe conventional Frequency Division Multiplexing (FDM) scheme, the OFDMscheme is distinguishable from conventional transmission schemes in thatOFDM can achieve optimal transmission efficiency during high-speed datatransmission by maintaining orthogonality between multiple sub-carriers.Also, the advantages of high frequency use efficiency and robustnessagainst multi-path fading contribute significantly to the optimaltransmission efficiency.

In addition, the OFDM transmission scheme, as it overlaps frequencyspectra, is efficiently uses frequencies, is robust against frequencyselective fading, can reduce influence of Inter-Symbol Interference(ISI) by using a guard interval, enables simple designs of hardwareequalizers, and is robust against impulsive noises. Thus, the OFDMtransmission scheme is widely used for communication systems.

Despite the advantages of the OFDM transmission scheme, themulti-carrier modulation of the OFDM transmission scheme causes a highPeak to Average Power Ratio (PAPR). Since the OFDM transmission schemetransmits data using multiple carriers, a final OFDM signal suffers asignificant change in amplitude as a level of its amplitude isdetermined by a sum of amplitude levels of the respective carriers. Whenthe carriers are equal in phase, the OFDM signal will have a very highamplitude. This high-PAPR signal may deviate from a linear operationrange of a high-power linear amplifier, and a signal that has passedthrough the high-power linear amplifier may often suffer fromdistortion, causing a reduction in system performance.

Various plans to solve the high-PAPR problem occurring in the OFDMsystem have been proposed, and the plans include several PAPR reductiontechniques, such as clipping, coding, SeLected Mapping (SLM), PartialTransmit Sequence (PTS), and Tone Injection (TI).

A Tone Reservation (TR) scheme, one of the PAPR reduction techniques,reserves some tones in sub-carriers, and the reserved tones are used toreduce PAPR instead of transmitting data. A receiver bypasses thereserved tones that do not carry information signals, and restoresinformation signals only in data tones other than the reserved tones,thus contributing to a simplified structure of the receiver. A gradientalgorithm is a typical one of the methods that reduce PAPR usingreserved tones in the TR scheme. The gradient algorithm is defined byapplying a method similar to the clipping technique to the TR scheme.The gradient algorithm is used to create a signal (or a kernel) havingan impulse characteristic using reserved tones that carry no informationsignal, and to clip off an output signal of an Inverse Fast FourierTransform (IFFT) unit. When the signal having an impulse characteristicis added to the output signal of the IFFT unit, distortion of dataoccurs only in the reserved tones, and data in other frequency regionsis not distorted, i.e., the TR scheme is different from the clippingtechnique in that the noise caused by clipping has an effect only onsome reserved sub-carriers without affecting all sub-carriers. Thegradient algorithm optimizes impulse waveforms so that a peak of an IFFToutput signal is reduced in the time domain. A signal, a PAPR of whichwas reduced by adding a sum of the impulse waveforms optimized by thegradient algorithm to the output signal of the IFFT unit, is transmittedto a receiver. The receiver only needs to receive data on the remainingsub-carriers since the receiver is notified of the locations of thereserved tones in advance.

FIG. 1 illustrates a structure of a transmitter to which a general TRscheme is applied.

Referring to FIG. 1, an input signal X 105 having N-L points (where Ndenotes a size of IFFT) and an L-reserved tone signal C 110 (a signalconsisting of L reserved tones) are input to a tone reservation unit120, and the tone reservation unit 120 reserves L reserved tones insub-carrier locations previously agreed between a transmitter and areceiver. The L reserved tones carry no data and have zeros (0s)inserted therein. When a sum of the parallel data X and the L reservedtones is input to an N-point IFFT unit 130, the input sum undergoes IFFTcomputation in the N-point IFFT unit 130, and then a time-domain outputsignal x is generated by a parallel-to-serial (P/S) conversion unit 140.Next, a gradient unit 150 creates a signal c by optimizing impulsewaveforms according to the gradient algorithm so that a peak of the IFFToutput signal is reduced, and adds the created signal c to the outputsignal x that has passed through the IFFT unit 130 and the P/Sconversion unit 140. The output signal of the gradient unit 150 istransmitted to the receiver. The gradient unit 150 calculates the signalc that is added to the output signal x so that PAPR of the output signalx is reduced, using impulse waveforms read from a memory 160. Forreference, uppercases X and C in FIG. 1 represent frequency-domainsignals being input to the IFFT unit 130, while lowercases x and crepresent time-domain signals output from the IFFT unit 130.

The signal c that is added to the output signal x to reduce PAPR in Lreserved tones, is determined as follows. L sub-carriers are reserved inadvance and used to determine a code C for calculation of the signal c,and locations of the L sub-carriers are fixed by the tone reservationunit 120 during initial transmission, and remain unchanged during datatransmission. The code C represents the reserved tone signal, and C_(k)represents sub-carrier locations of reserved tones as defined inEquation (1) below.

$\begin{matrix}{C_{k} = \{ \begin{matrix}{C_{k},} & {k \in \{ {i_{1},i_{2},\ldots \mspace{14mu},i_{L}} \}} \\{0,} & {k \notin \{ {i_{1},i_{2},\ldots \mspace{14mu},i_{L}} \}}\end{matrix} } & (1)\end{matrix}$

where k denotes sub-carrier indexes of reserved tones in the tonereservation unit 110. The input signal X 105 is reserved in sub-carriersaside from the reserved tone signal C 110 as shown in Equation (2).

$\begin{matrix}{X_{k} = \{ \begin{matrix}{X_{k},} & {k \notin \{ {i_{1},i_{2},\ldots \mspace{14mu},i_{L}} \}} \\{0,} & {k \in \{ {i_{1},i_{2},\ldots \mspace{14mu},i_{L}} \}}\end{matrix} } & (2)\end{matrix}$

where X_(k) denotes sub-carrier locations of data tones.

PAPR minimization is achieved by optimizing amplitudes of the Lsub-carriers. {tilde over (C)} for PAPR minimization is optimized byEquation (3) below such that PAPR of an output signal x is reduced.Here, {tilde over (C)} corresponds to the signal c.

$\begin{matrix}{\overset{\sim}{C} = {{Arg}{\min\limits_{\overset{\_}{C}}( {\max\limits_{n = {{0\mspace{14mu} \ldots \mspace{14mu} N} - 1}}{{x_{n} + c_{n}}}} )}}} & (3)\end{matrix}$

where C_(n) is a value of an n-th element in a time-domain vector cdetermined by IFFT-processing a vector C. Computation of Equation (3) isperformed to find an optimized signal for the signal c. Although complexlinear computation is conducted to solve Equation (3), the gradientalgorithm is performed in actual implementations, which can achieve thesimilar performance through simple computations.

The signal c is optimized to remove a peak-to-peak value of a vector x(i.e., an output signal). If x^(clip) is assumed to be a vector where anoutput signal x is clipped to a certain level A, then Equation (4) isderived.

x−x ^(clip)=Σ_(i)β_(i) δ[n−m _(i)]  (4)

where β_(i) denotes a clipping value, m_(i) denotes a location where thevector is clipped, and δ denotes an impulse function.

If the signal c is defined as Equation (5), Equation (6) can be derivedand a peak-to-peak value of a transmission symbol can be reduced.

c=−Σ _(i)β_(i) δ[n−m _(i)]  (5)

x+c=x ^(clip)   (6)

Therefore, the signal c added to the output signal x can be construed asa sum of delayed and scaled impulse functions. However, in a frequencydomain, {tilde over (C)}=FFT(c) has a non-zero value at mostfrequencies, and distorts values of data symbols in locations other thanthe reserved L locations. Thus, there is a need to use, for clipping,waveforms having characteristics of an impulse function, which areaffected only in the L reserved locations but not affected in otherlocations in the frequency domain.

Waveforms having impulse characteristics are designed as follows.

Assume that 1_(L) represents a vector having a value of 1 in L reservedlocations and a value of 0 in other locations, and p is defined asEquation (7).

$\begin{matrix}{p = {{p\lbrack n\rbrack} = {\lbrack {p_{0}p_{1}\mspace{14mu} \ldots \mspace{14mu} p_{N - 1}} \rbrack = {\frac{\sqrt{N}}{L}I\; F\; F\; {T( 1_{L} )}}}}} & (7)\end{matrix}$

In Equation (7), p₀=1, and p₁ . . . p_(N-1) have significantly smallvalues compared to p₀. Assuming that p[((n−m_(i)))_(N)] indicates avalue determined by cyclic-shifting p by m_(i), even though DiscreteFourier Transform (DFT) is performed thereon, the resulting valuechanges only in phase and has a value of 0 in locations other than the Lreserved locations in the frequency domain.

As described above, the waveforms having impulse characteristics aredesigned such that amplitudes of the remaining p₁ . . . p_(N-1) exceptfor p₀ are low, in order for the waveforms to become similar to idealimpulse waveforms. As amplitudes of p₁ . . . p_(N-1) are lower, a changein amplitudes of other signals except for p₀ is less significant duringclipping. If the design is made such that p₁ . . . p_(N-1) have highamplitudes, peaks of other signals may increase again in the clippingprocess, thereby causing a reduction in PAPR reduction performance.

FIG. 2 illustrates a frame structure for a physical layer of a generalDVB system using OFDM.

A frame structure 201 of FIG. 2 can be roughly divided into preambleparts 202 and 203, and a payload part 204. The preamble parts 202 and203 carry signaling information of the frame, and the payload part 204is used to transmit data.

The P1 preamble 202 is used at a receiver to scan an initial signal ofthe frame. Further, the P1 preamble 202 is used to detect a frequencyoffset and tune the center frequency. Next, the P2 preamble 203 is usedto provide Layer 1 (L1) signaling of the DVB system. The L1 signalingincludes such information as transmission types, transmissionparameters, etc. of the DVB system. Finally, the payload 204 carriesservice data provided in the DVB system.

In the communication system that uses the OFDM transmission scheme andtransmits the frame including preambles, it is important to reduce PAPRin order to improve the system performance, and the high-PAPR problemoccurs not only in the payload part in which data is transmitted, butalso in the preamble parts in which signaling information istransmitted, in the physical layer frame. Therefore, there is a need forreducing PAPR, including reducing PAPR in the preamble parts of a frame.

SUMMARY OF THE INVENTION

The present invention has been designed to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention provides a transmission method and apparatus capable ofreducing PAPR of a preamble in an OFDM system.

Another aspect of the present invention provides a transmission methodand apparatus capable of reducing PAPR of a preamble in a digitalbroadcasting system using an OFDM transmission scheme.

Another aspect of the present invention provides PAPR reductionapparatus and method suitable for a preamble structure in a digitalbroadcasting system.

Another aspect of the present invention provides a transmissionapparatus and method for determining locations of reserved tones usedfor PAPR reduction in a preamble in a digital broadcasting system.

In accordance with an aspect of the present invention, a method isprovided for reducing a Peak to Average Power Ratio (PAPR) in a digitalbroadcasting system. Determined reserved tones are used to transmit asignal having an impulse characteristic in locations of sub-carriersthat do not collide with a pilot signal of a preamble in a frame. Thesignal having the impulse characteristic is transmitted through thereserved tones in a symbol period for which the preamble is transmitted.

In accordance with another aspect of the present invention, atransmission apparatus is provided for reducing a Peak to Average PowerRatio (PAPR) in a digital broadcasting system. A tone reservation unitdetermines reserved tones used to transmit a signal having an impulsecharacteristic in locations of sub-carriers that do not collide with apilot signal of a preamble in a frame. A transmission unit transmits thesignal having the impulse characteristic through the reserved tones in asymbol period for which the preamble is transmitted.

In accordance with further another aspect of the present invention, atransmission apparatus is provided for reducing a Peak to Average PowerRatio (PAPR) in a digital broadcasting system. A transmission unittransmits a frame in which a preamble is included. A memory storesindexes of reserved tones used to transmit a signal having an impulsecharacteristic in locations of sub-carriers that do not collide with apilot signal of the preamble. A controller generates the signal havingthe impulse characteristic according to the indexes of the reservedtones and controls the transmission unit to transmit the signal havingthe impulse characteristic through the reserved tones in a symbol periodfor which the preamble is transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a structure of a TR-based transmitter;

FIG. 2 illustrates a frame structure of a DVB system;

FIG. 3 illustrates a structure of an OFDM symbol carrying a P2 preamblein a DVB system according to an embodiment of the present invention; and

FIG. 4 illustrates a waveform having an impulse characteristicdetermined by reserved tones in a digital broadcasting system accordingto an embodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of embodiments ofthe present invention. Accordingly, the description includes variousspecific details to assist in that understanding but these are to beregarded as merely exemplary. Further, those of ordinary skill in theart will recognize that various changes and modifications of theembodiments described herein can be made without departing from thescope and spirit of the invention. In addition, descriptions ofwell-known functions and constructions are omitted for clarity andconciseness.

The terms and words used in the following description and claims are notlimited to dictionary meanings, but are merely used by the inventor toenable a clear and consistent understanding of the invention. It shouldbe apparent to those skilled in the art that the following descriptionof exemplary embodiments of the present invention are provided forillustration purpose only and not for the purpose of limiting thepresent invention as defined by the appended claims and theirequivalents.

In the following description, a method and apparatus for reducing PAPRof a preamble will be described in connection with a digitalbroadcasting system such as a DVB system for convenience purpose only.However, the present invention can be equally applied to anycommunication system that uses an OFDM transmission scheme and transmitsa frame having a structure in which preambles are included.

The preamble structure described in FIG. 2 is an example of a preamblestructure to which the present invention is applicable, and it is notintended to limit the scope of the present invention to the particularpreamble structure. For example, the present invention can be applied toany preamble structure that can be divided into one preamble part ordivided into two or more preamble parts.

As described above, there is a need to reduce PAPR of a preamble in adigital broadcasting system. For PAPR reduction, a DVB system mayreserve some sub-carriers for a P2 preamble to employ a TR scheme amongseveral PAPR reduction techniques. Thus, reserved tones may be designedin accordance with the P2 preamble structure.

In a digital broadcasting system employing the TR scheme, reserved tonesmust not collide with a pilot, and determined such that waveforms havingimpulse characteristics that occur due to the reserved tones aresuitable for PAPR reduction. This is because locations of the reservedtones have an influence on PAPR performance.

FIG. 3 illustrates an OFDM symbol carrying a P2 preamble in a digitalbroadcasting system according to an exemplary embodiment of the presentinvention.

Referring to FIG. 3, sub-carriers for transmission of an OFDM symbol aredivided into a pilot part 301 for channel estimation and a data part 302through which signaling information is transmitted. The pilot part 301exists in the locations determined by Equation (8).

k mod 3=0   (8)

where k denotes a sub-carrier index, and ‘mod’ represents a moduleoperation. In accordance with Equation (8), a pilot tone is located inevery third sub-carrier in the frequency domain.

The digital broadcasting system, to which the present invention isapplied, supports a plurality of Fast Fourier Transform (FFT) modes(e.g., 1K, 2K, 4K, 8K, 16K, and 32K), and a P2 preamble exists in eachFFT mode. In the digital broadcasting system, the number of OFDM symbolscarrying a P2 preamble is determined according to each of the FFT modes,and Table 1 below illustrates the number of OFDM symbols for each FFTmode.

TABLE 1 FFT mode Number of OFDM symbols 1K 16 2K 8 4K 4 8K 2 16K  1 32K 1

Referring to Table 1, a P2 preamble is transmitted for a 16-OFDM symbolperiod in a 1K FFT mode, and for a 1-OFDM symbol period in 16K and 32KFFT modes.

The TR scheme for reducing PAPR in the P2 preamble of the digitalbroadcasting system may use some of data sub-carriers through whichsignaling information is transmitted. In application of the TR scheme,it is important how to design the reserved tones since PAPR reductionperformance depends on the reserved tones.

That is, locations of reserved tones in the P2 preamble 203 of FIG. 2should be designed not to collide with a pilot signal (or pilot tones)for channel estimation, and waveforms having impulse characteristicscaused by the reserved tones must be designed to be suitable for PAPRreduction. In other words, locations of the reserved tones must bedetermined in Equation (7) such that p₁ . . . p_(N-1) have small values.

The number of and locations of reserved tones for reducing PAPR of a P2preamble, proposed by the present invention, are shown in Table 2 andTable 3. The number of reserved tones differs according to FFT size, thereserved tones are designed not to collide with a pilot signal (or pilottones), and the waveforms having impulse characteristics are designed tohave good PAPR reduction performance.

Table 2 shows the number of and indexes of reserved tones for 1K, 2K,and 4K FFT modes, and Table 3 shows the number of and indexes ofreserved tones for 8K, 16K, and 32K FFT modes.

TABLE 2 FFT mode (Number of reserved tones) Indexes of Reserved tones 1K(10) 116, 130, 134, 157, 182, 256, 346, 478, 479, 532 2K (18) 113, 124,262, 467, 479, 727, 803, 862, 910, 946, 980, 1201, 1322, 1342, 1396,1397, 1562, 1565 4K (36) 104, 116, 119, 163, 170, 664, 886, 1064, 1151,1196, 1264, 1531, 1736, 1951, 1960, 2069, 2098, 2311, 2366, 2473, 2552,2584, 2585, 2645, 2774, 2846, 2882, 3004, 3034, 3107, 3127, 3148, 3191,3283, 3289

TABLE 3 FFT mode (Number of reserved tones) Indexes of reserved tones 8K (72) 106, 109, 110, 112, 115, 118, 133, 142, 163, 184, 206, 247,445, 461, 503, 565, 602, 656, 766, 800, 922, 1094, 1108, 1199, 1258,1726, 1793, 1939, 2128, 2714, 3185, 3365, 3541, 3655, 3770, 3863, 4066,4190, 4282, 4565, 4628, 4727, 4882, 4885, 5143, 5192, 5210, 5257, 5261,5459, 5651, 5809, 5830, 5986, 6020, 6076, 6253, 6269, 6410, 6436, 6467,6475, 6509, 6556, 6611, 6674, 6685, 6689, 6691, 6695, 6698, 6701 16K(144) 104, 106, 107, 109, 110, 112, 113, 115, 116, 118, 119, 121, 122,125, 128, 131, 134, 137, 140, 143, 161, 223, 230, 398, 482, 497, 733,809, 850, 922, 962, 1196, 1256, 1262, 1559, 1691, 1801, 1819, 1937,2005, 2095, 2308, 2383, 2408, 2425, 2428, 2479, 2579, 2893, 2902, 3086,3554, 4085, 4127, 4139, 4151, 4163, 4373, 4400, 4576, 4609, 4952, 4961,5444, 5756, 5800, 6094, 6208, 6658, 6673, 6799, 7208, 7682, 8101, 8135,8230, 8692, 8788, 8933, 9323, 9449, 9478, 9868, 10192, 10261, 10430,10630, 10685, 10828, 10915, 10930, 10942, 11053, 11185, 11324, 11369,11468, 11507, 11542, 11561, 11794, 11912, 11974, 11978, 12085, 12179,12193, 12269, 12311, 12758, 12767, 12866, 12938, 12962, 12971, 13099,13102, 13105, 13120, 13150, 13280, 13282, 13309, 13312, 13321, 13381,13402, 13448, 13456, 13462, 13463, 13466, 13478, 13492, 13495, 13498,13501, 13502, 13504, 13507, 13510, 13513, 13514, 13516 32K (288) 104,106, 107, 109, 110, 112, 113, 115, 118, 121, 124, 127, 130, 133, 136,139, 142, 145, 148, 151, 154, 157, 160, 163, 166, 169, 172, 175, 178,181, 184, 187, 190, 193, 196, 199, 202, 205, 208, 211, 404, 452, 455,467, 509, 539, 568, 650, 749, 1001, 1087, 1286, 1637, 1823, 1835, 1841,1889, 1898, 1901, 2111, 2225, 2252, 2279, 2309, 2315, 2428, 2452, 2497,2519, 3109, 3154, 3160, 3170, 3193, 3214, 3298, 3331, 3346, 3388, 3397,3404, 3416, 3466, 3491, 3500, 3572, 4181, 4411, 4594, 4970, 5042, 5069,5081, 5086, 5095, 5104, 5320, 5465, 5491, 6193, 6541, 6778, 6853, 6928,6934, 7030, 7198, 7351, 7712, 7826, 7922, 8194, 8347, 8350, 8435, 8518,8671, 8861, 8887, 9199, 9980, 10031, 10240, 10519, 10537, 10573, 10589,11078, 11278, 11324, 11489, 11642, 12034, 12107, 12184, 12295, 12635,12643, 12941, 12995, 13001, 13133, 13172, 13246, 13514, 13522, 13939,14362, 14720, 14926, 15338, 15524, 15565, 15662, 15775, 16358, 16613,16688, 16760, 17003, 17267, 17596, 17705, 18157, 18272, 18715, 18994,19249, 19348, 20221, 20855, 21400, 21412, 21418, 21430, 21478, 21559,21983, 21986, 22331, 22367, 22370, 22402, 22447, 22535, 22567, 22571,22660, 22780, 22802, 22844, 22888, 22907, 23021, 23057, 23086, 23213,23240, 23263, 23333, 23369, 23453, 23594, 24143, 24176, 24319, 24325,24565, 24587, 24641, 24965, 25067, 25094, 25142, 25331, 25379, 25465,25553, 25589, 25594, 25655, 25664, 25807, 25823, 25873, 25925, 25948,26002, 26008, 26102, 26138, 26141, 26377, 26468, 26498, 26510, 26512,26578, 26579, 26588, 26594, 26597, 26608, 26627, 26642, 26767, 26776,26800, 26876, 26882, 26900, 26917, 26927, 26951, 26957, 26960, 26974,26986, 27010, 27013, 27038, 27044, 27053, 27059, 27061, 27074, 27076,27083, 27086, 27092, 27094, 27098, 27103, 27110, 27115, 27118, 27119,27125, 27128, 27130, 27133, 27134, 27140, 27143, 27145, 27146, 27148,27149

The structure of FIG. 1 can be used as a transmitter to which the TRscheme according to an embodiment of the present invention is applied.As one example, the tone reservation unit 120 reserves reserved tones totransmit a signal having an impulse characteristic in locations ofsub-carriers that do not collide with a pilot signal of a preamble in aframe (e.g., in sub-carrier locations previously agreed between atransmitter and a receiver as shown in Table 2 and/or Table 3 inaccordance with the reserved tone indexes for respective FFT modes). Asanother example of the transmitter structure, the tone reservation unit120 and the gradient unit 150 may be formed as a controller (not shown).

FIG. 4 illustrates a waveform having an impulse characteristic of a P2preamble in a digital broadcasting system according to an exemplaryembodiment of the present invention. Performance of a waveform having animpulse characteristic can be represented by a ratio of power of p₀ tothe highest power among powers of p₁˜P_(N-1) in Equation (7). Here, p₀indicates the primary peak, while the highest power among the powers ofthe remaining p₁˜p_(N-1) is called the secondary peak, which is setlower than the primary peak.

Table 4 below shows the secondary peak for the reserved tones designedin Table 2 and Table 3.

TABLE 4 FFT mode Secondary peak [dB] 1K −4.3199 2K −6.5913 4K −9.1721 8K−10.4574 16K  −10.8517 32K  −10.9473

Referring to Table 4, when locations of the reserved tones for 8K, 16K,and 32K FFT modes are set as shown in Table 3, values of the secondarypeaks are significantly reduced.

As is apparent from the foregoing description, the present invention canreduce PAPR of a preamble while preventing the preamble from collidingwith a pilot signal in a digital broadcasting system.

In addition, the present invention can provide reserved tones havinggood PAPR reduction performance for a preamble in a digital broadcastingsystem.

Embodiments of the present invention can also be embodied ascomputer-readable codes on a computer-readable recording medium.Computer-readable recording mediums include any data storage device thatcan store data, which can thereafter be read by a computer system.Examples of the computer-readable recording mediums include, but are notlimited to, Read-Only Memory (ROM), Random-Access Memory (RAM), CompactDisc (CD)-ROMs, magnetic tapes, floppy disks, optical data storagedevices, and carrier waves (such as data transmission through theInternet via wired or wireless transmission paths). Computer-readablerecording mediums can also be distributed over network-coupled computersystems so that the computer-readable code is stored and executed in adistributed fashion. Also, function programs, codes, and code segmentsfor accomplishing the present invention can be easily construed aswithin the scope of the invention by programmers skilled in the art towhich the present invention pertains.

While the invention has been shown and described with reference to acertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

1. A method for reducing a Peak to Average Power Ratio (PAPR) in adigital broadcasting system, comprising: determining reserved tones usedto transmit a signal having an impulse characteristic in locations ofsub-carriers that do not collide with a pilot signal of a preamble in aframe; and transmitting the signal having the impulse characteristicthrough the reserved tones in a symbol period for which the preamble istransmitted.
 2. The method of claim 1, wherein the digital broadcastingsystem uses Orthogonal Frequency Division Multiplexing (OFDM) as atransmission scheme, and locations of the reserved tones vary accordingto a Fast Fourier Transform (FFT) size.
 3. The method of claim 2,wherein when the FFT size is 8K, locations of the reserved tones aredetermined in accordance with the following table: FFT mode (Number ofreserved tones) Indexes of reserved tones 8K (72) 106, 109, 110, 112,115, 118, 133, 142, 163, 184, 206, 247, 445, 461, 503, 565, 602, 656,766, 800, 922, 1094, 1108, 1199, 1258, 1726, 1793, 1939, 2128, 2714,3185, 3365, 3541, 3655, 3770, 3863, 4066, 4190, 4282, 4565, 4628, 4727,4882, 4885, 5143, 5192, 5210, 5257, 5261, 5459, 5651, 5809, 5830, 5986,6020, 6076, 6253, 6269, 6410, 6436, 6467, 6475, 6509, 6556, 6611, 6674,6685, 6689, 6691, 6695, 6698, 6701


4. The method of claim 2, wherein when the FFT size is 16K, locations ofthe reserved tones are determined in accordance with the followingtable: FFT mode (Number of reserved tones) Indexes of reserved tones 16K(144) 104, 106, 107, 109, 110, 112, 113, 115, 116, 118, 119, 121, 122,125, 128, 131, 134, 137, 140, 143, 161, 223, 230, 398, 482, 497, 733,809, 850, 922, 962, 1196, 1256, 1262, 1559, 1691, 1801, 1819, 1937,2005, 2095, 2308, 2383, 2408, 2425, 2428, 2479, 2579, 2893, 2902, 3086,3554, 4085, 4127, 4139, 4151, 4163, 4373, 4400, 4576, 4609, 4952, 4961,5444, 5756, 5800, 6094, 6208, 6658, 6673, 6799, 7208, 7682, 8101, 8135,8230, 8692, 8788, 8933, 9323, 9449, 9478, 9868, 10192, 10261, 10430,10630, 10685, 10828, 10915, 10930, 10942, 11053, 11185, 11324, 11369,11468, 11507, 11542, 11561, 11794, 11912, 11974, 11978, 12085, 12179,12193, 12269, 12311, 12758, 12767, 12866, 12938, 12962, 12971, 13099,13102, 13105, 13120, 13150, 13280, 13282, 13309, 13312, 13321, 13381,13402, 13448, 13456, 13462, 13463, 13466, 13478, 13492, 13495, 13498,13501, 13502, 13504, 13507, 13510, 13513, 13514, 13516


5. The method of claim 2, wherein when the FFT size is 32K, locations ofthe reserved tones are determined in accordance with the followingtable: FFT mode (Number of reserved tones) Indexes of reserved tones 32K(288) 104, 106, 107, 109, 110, 112, 113, 115, 118, 121, 124, 127, 130,133, 136, 139, 142, 145, 148, 151, 154, 157, 160, 163, 166, 169, 172,175, 178, 181, 184, 187, 190, 193, 196, 199, 202, 205, 208, 211, 404,452, 455, 467, 509, 539, 568, 650, 749, 1001, 1087, 1286, 1637, 1823,1835, 1841, 1889, 1898, 1901, 2111, 2225, 2252, 2279, 2309, 2315, 2428,2452, 2497, 2519, 3109, 3154, 3160, 3170, 3193, 3214, 3298, 3331, 3346,3388, 3397, 3404, 3416, 3466, 3491, 3500, 3572, 4181, 4411, 4594, 4970,5042, 5069, 5081, 5086, 5095, 5104, 5320, 5465, 5491, 6193, 6541, 6778,6853, 6928, 6934, 7030, 7198, 7351, 7712, 7826, 7922, 8194, 8347, 8350,8435, 8518, 8671, 8861, 8887, 9199, 9980, 10031, 10240, 10519, 10537,10573, 10589, 11078, 11278, 11324, 11489, 11642, 12034, 12107, 12184,12295, 12635, 12643, 12941, 12995, 13001, 13133, 13172, 13246, 13514,13522, 13939, 14362, 14720, 14926, 15338, 15524, 15565, 15662, 15775,16358, 16613, 16688, 16760, 17003, 17267, 17596, 17705, 18157, 18272,18715, 18994, 19249, 19348, 20221, 20855, 21400, 21412, 21418, 21430,21478, 21559, 21983, 21986, 22331, 22367, 22370, 22402, 22447, 22535,22567, 22571, 22660, 22780, 22802, 22844, 22888, 22907, 23021, 23057,23086, 23213, 23240, 23263, 23333, 23369, 23453, 23594, 24143, 24176,24319, 24325, 24565, 24587, 24641, 24965, 25067, 25094, 25142, 25331,25379, 25465, 25553, 25589, 25594, 25655, 25664, 25807, 25823, 25873,25925, 25948, 26002, 26008, 26102, 26138, 26141, 26377, 26468, 26498,26510, 26512, 26578, 26579, 26588, 26594, 26597, 26608, 26627, 26642,26767, 26776, 26800, 26876, 26882, 26900, 26917, 26927, 26951, 26957,26960, 26974, 26986, 27010, 27013, 27038, 27044, 27053, 27059, 27061,27074, 27076, 27083, 27086, 27092, 27094, 27098, 27103, 27110, 27115,27118, 27119, 27125, 27128, 27130, 27133, 27134, 27140, 27143, 27145,27146, 27148, 27149


6. The method of claim 2, wherein when OFDM supports a plurality of FFTsizes, locations of the reserved tones are determined in accordance withthe following table: FFT mode (Number of reserved tones) Indexes ofreserved tones  8K (72) 106, 109, 110, 112, 115, 118, 133, 142, 163,184, 206, 247, 445, 461, 503, 565, 602, 656, 766, 800, 922, 1094, 1108,1199, 1258, 1726, 1793, 1939, 2128, 2714, 3185, 3365, 3541, 3655, 3770,3863, 4066, 4190, 4282, 4565, 4628, 4727, 4882, 4885, 5143, 5192, 5210,5257, 5261, 5459, 5651, 5809, 5830, 5986, 6020, 6076, 6253, 6269, 6410,6436, 6467, 6475, 6509, 6556, 6611, 6674, 6685, 6689, 6691, 6695, 6698,6701 16K (144) 104, 106, 107, 109, 110, 112, 113, 115, 116, 118, 119,121, 122, 125, 128, 131, 134, 137, 140, 143, 161, 223, 230, 398, 482,497, 733, 809, 850, 922, 962, 1196, 1256, 1262, 1559, 1691, 1801, 1819,1937, 2005, 2095, 2308, 2383, 2408, 2425, 2428, 2479, 2579, 2893, 2902,3086, 3554, 4085, 4127, 4139, 4151, 4163, 4373, 4400, 4576, 4609, 4952,4961, 5444, 5756, 5800, 6094, 6208, 6658, 6673, 6799, 7208, 7682, 8101,8135, 8230, 8692, 8788, 8933, 9323, 9449, 9478, 9868, 10192, 10261,10430, 10630, 10685, 10828, 10915, 10930, 10942, 11053, 11185, 11324,11369, 11468, 11507, 11542, 11561, 11794, 11912, 11974, 11978, 12085,12179, 12193, 12269, 12311, 12758, 12767, 12866, 12938, 12962, 12971,13099, 13102, 13105, 13120, 13150, 13280, 13282, 13309, 13312, 13321,13381, 13402, 13448, 13456, 13462, 13463, 13466, 13478, 13492, 13495,13498, 13501, 13502, 13504, 13507, 13510, 13513, 13514, 13516 32K (288)104, 106, 107, 109, 110, 112, 113, 115, 118, 121, 124, 127, 130, 133,136, 139, 142, 145, 148, 151, 154, 157, 160, 163, 166, 169, 172, 175,178, 181, 184, 187, 190, 193, 196, 199, 202, 205, 208, 211, 404, 452,455, 467, 509, 539, 568, 650, 749, 1001, 1087, 1286, 1637, 1823, 1835,1841, 1889, 1898, 1901, 2111, 2225, 2252, 2279, 2309, 2315, 2428, 2452,2497, 2519, 3109, 3154, 3160, 3170, 3193, 3214, 3298, 3331, 3346, 3388,3397, 3404, 3416, 3466, 3491, 3500, 3572, 4181, 4411, 4594, 4970, 5042,5069, 5081, 5086, 5095, 5104, 5320, 5465, 5491, 6193, 6541, 6778, 6853,6928, 6934, 7030, 7198, 7351, 7712, 7826, 7922, 8194, 8347, 8350, 8435,8518, 8671, 8861, 8887, 9199, 9980, 10031, 10240, 10519, 10537, 10573,10589, 11078, 11278, 11324, 11489, 11642, 12034, 12107, 12184, 12295,12635, 12643, 12941, 12995, 13001, 13133, 13172, 13246, 13514, 13522,13939, 14362, 14720, 14926, 15338, 15524, 15565, 15662, 15775, 16358,16613, 16688, 16760, 17003, 17267, 17596, 17705, 18157, 18272, 18715,18994, 19249, 19348, 20221, 20855, 21400, 21412, 21418, 21430, 21478,21559, 21983, 21986, 22331, 22367, 22370, 22402, 22447, 22535, 22567,22571, 22660, 22780, 22802, 22844, 22888, 22907, 23021, 23057, 23086,23213, 23240, 23263, 23333, 23369, 23453, 23594, 24143, 24176, 24319,24325, 24565, 24587, 24641, 24965, 25067, 25094, 25142, 25331, 25379,25465, 25553, 25589, 25594, 25655, 25664, 25807, 25823, 25873, 25925,25948, 26002, 26008, 26102, 26138, 26141, 26377, 26468, 26498, 26510,26512, 26578, 26579, 26588, 26594, 26597, 26608, 26627, 26642, 26767,26776, 26800, 26876, 26882, 26900, 26917, 26927, 26951, 26957, 26960,26974, 26986, 27010, 27013, 27038, 27044, 27053, 27059, 27061, 27074,27076, 27083, 27086, 27092, 27094, 27098, 27103, 27110, 27115, 27118,27119, 27125, 27128, 27130, 27133, 27134, 27140, 27143, 27145, 27146,27148, 27149


7. The method of claim 1, wherein the preamble comprises a P2 symbolthat carries signaling information of a physical layer in a DVB system.8. The method of claim 1, wherein transmitting the signal having theimpulse characteristic further comprises adding the signal having theimpulse characteristic to an information signal that is transmittedthrough data tones in the preamble, using a gradient algorithm for PAPRreduction.
 9. A transmission apparatus for reducing a Peak to AveragePower Ratio (PAPR) in a digital broadcasting system, comprising: a tonereservation unit for determining reserved tones used to transmit asignal having an impulse characteristic in locations of sub-carriersthat do not collide with a pilot signal of a preamble in a frame; and atransmission unit for transmitting the signal having the impulsecharacteristic through the reserved tones in a symbol period for whichthe preamble is transmitted.
 10. The transmission apparatus of claim 9,wherein the digital broadcasting system uses Orthogonal FrequencyDivision Multiplexing (OFDM) as a transmission scheme, and locations ofthe reserved tones vary according to a Fast Fourier Transform (FFT)size.
 11. The transmission apparatus of claim 10, wherein when the FFTsize is 8K, locations of the reserved tones are determined in accordancewith the following table: FFT mode (Number of reserved tones) Indexes ofreserved tones 8K (72) 106, 109, 110, 112, 115, 118, 133, 142, 163, 184,206, 247, 445, 461, 503, 565, 602, 656, 766, 800, 922, 1094, 1108, 1199,1258, 1726, 1793, 1939, 2128, 2714, 3185, 3365, 3541, 3655, 3770, 3863,4066, 4190, 4282, 4565, 4628, 4727, 4882, 4885, 5143, 5192, 5210, 5257,5261, 5459, 5651, 5809, 5830, 5986, 6020, 6076, 6253, 6269, 6410, 6436,6467, 6475, 6509, 6556, 6611, 6674, 6685, 6689, 6691, 6695, 6698, 6701


12. The transmission apparatus of claim 10, wherein when the FFT size is16K, locations of the reserved tones are determined in accordance withthe following table: FFT mode (Number of reserved tones) Indexes ofreserved tones 16K (144) 104, 106, 107, 109, 110, 112, 113, 115, 116,118, 119, 121, 122, 125, 128, 131, 134, 137, 140, 143, 161, 223, 230,398, 482, 497, 733, 809, 850, 922, 962, 1196, 1256, 1262, 1559, 1691,1801, 1819, 1937, 2005, 2095, 2308, 2383, 2408, 2425, 2428, 2479, 2579,2893, 2902, 3086, 3554, 4085, 4127, 4139, 4151, 4163, 4373, 4400, 4576,4609, 4952, 4961, 5444, 5756, 5800, 6094, 6208, 6658, 6673, 6799, 7208,7682, 8101, 8135, 8230, 8692, 8788, 8933, 9323, 9449, 9478, 9868, 10192,10261, 10430, 10630, 10685, 10828, 10915, 10930, 10942, 11053, 11185,11324, 11369, 11468, 11507, 11542, 11561, 11794, 11912, 11974, 11978,12085, 12179, 12193, 12269, 12311, 12758, 12767, 12866, 12938, 12962,12971, 13099, 13102, 13105, 13120, 13150, 13280, 13282, 13309, 13312,13321, 13381, 13402, 13448, 13456, 13462, 13463, 13466, 13478, 13492,13495, 13498, 13501, 13502, 13504, 13507, 13510, 13513, 13514, 13516


13. The transmission apparatus of claim 10, wherein when the FFT size is32K, locations of the reserved tones are determined in accordance withthe following table: FFT mode (Number of reserved tones) Indexes ofreserved tones 32K (288) 104, 106, 107, 109, 110, 112, 113, 115, 118,121, 124, 127, 130, 133, 136, 139, 142, 145, 148, 151, 154, 157, 160,163, 166, 169, 172, 175, 178, 181, 184, 187, 190, 193, 196, 199, 202,205, 208, 211, 404, 452, 455, 467, 509, 539, 568, 650, 749, 1001, 1087,1286, 1637, 1823, 1835, 1841, 1889, 1898, 1901, 2111, 2225, 2252, 2279,2309, 2315, 2428, 2452, 2497, 2519, 3109, 3154, 3160, 3170, 3193, 3214,3298, 3331, 3346, 3388, 3397, 3404, 3416, 3466, 3491, 3500, 3572, 4181,4411, 4594, 4970, 5042, 5069, 5081, 5086, 5095, 5104, 5320, 5465, 5491,6193, 6541, 6778, 6853, 6928, 6934, 7030, 7198, 7351, 7712, 7826, 7922,8194, 8347, 8350, 8435, 8518, 8671, 8861, 8887, 9199, 9980, 10031,10240, 10519, 10537, 10573, 10589, 11078, 11278, 11324, 11489, 11642,12034, 12107, 12184, 12295, 12635, 12643, 12941, 12995, 13001, 13133,13172, 13246, 13514, 13522, 13939, 14362, 14720, 14926, 15338, 15524,15565, 15662, 15775, 16358, 16613, 16688, 16760, 17003, 17267, 17596,17705, 18157, 18272, 18715, 18994, 19249, 19348, 20221, 20855, 21400,21412, 21418, 21430, 21478, 21559, 21983, 21986, 22331, 22367, 22370,22402, 22447, 22535, 22567, 22571, 22660, 22780, 22802, 22844, 22888,22907, 23021, 23057, 23086, 23213, 23240, 23263, 23333, 23369, 23453,23594, 24143, 24176, 24319, 24325, 24565, 24587, 24641, 24965, 25067,25094, 25142, 25331, 25379, 25465, 25553, 25589, 25594, 25655, 25664,25807, 25823, 25873, 25925, 25948, 26002, 26008, 26102, 26138, 26141,26377, 26468, 26498, 26510, 26512, 26578, 26579, 26588, 26594, 26597,26608, 26627, 26642, 26767, 26776, 26800, 26876, 26882, 26900, 26917,26927, 26951, 26957, 26960, 26974, 26986, 27010, 27013, 27038, 27044,27053, 27059, 27061, 27074, 27076, 27083, 27086, 27092, 27094, 27098,27103, 27110, 27115, 27118, 27119, 27125, 27128, 27130, 27133, 27134,27140, 27143, 27145, 27146, 27148, 27149


14. The transmission apparatus of claim 10, wherein when OFDM supports aplurality of FFT sizes, locations of the reserved tones are determinedin accordance with the following table: FFT mode (Number of reservedtones) Indexes of reserved tones 8K (72) 106, 109, 110, 112, 115, 118,133, 142, 163, 184, 206, 247, 445, 461, 503, 565, 602, 656, 766, 800,922, 1094, 1108, 1199, 1258, 1726, 1793, 1939, 2128, 2714, 3185, 3365,3541, 3655, 3770, 3863, 4066, 4190, 4282, 4565, 4628, 4727, 4882, 4885,5143, 5192, 5210, 5257, 5261, 5459, 5651, 5809, 5830, 5986, 6020, 6076,6253, 6269, 6410, 6436, 6467, 6475, 6509, 6556, 6611, 6674, 6685, 6689,6691, 6695, 6698, 6701 16K (144) 104, 106, 107, 109, 110, 112, 113, 115,116, 118, 119, 121, 122, 125, 128, 131, 134, 137, 140, 143, 161, 223,230, 398, 482, 497, 733, 809, 850, 922, 962, 1196, 1256, 1262, 1559,1691, 1801, 1819, 1937, 2005, 2095, 2308, 2383, 2408, 2425, 2428, 2479,2579, 2893, 2902, 3086, 3554, 4085, 4127, 4139, 4151, 4163, 4373, 4400,4576, 4609, 4952, 4961, 5444, 5756, 5800, 6094, 6208, 6658, 6673, 6799,7208, 7682, 8101, 8135, 8230, 8692, 8788, 8933, 9323, 9449, 9478, 9868,10192, 10261, 10430, 10630, 10685, 10828, 10915, 10930, 10942, 11053,11185, 11324, 11369, 11468, 11507, 11542, 11561, 11794, 11912, 11974,11978, 12085, 12179, 12193, 12269, 12311, 12758, 12767, 12866, 12938,12962, 12971, 13099, 13102, 13105, 13120, 13150, 13280, 13282, 13309,13312, 13321, 13381, 13402, 13448, 13456, 13462, 13463, 13466, 13478,13492, 13495, 13498, 13501, 13502, 13504, 13507, 13510, 13513, 13514,13516 32K (288) 104, 106, 107, 109, 110, 112, 113, 115, 118, 121, 124,127, 130, 133, 136, 139, 142, 145, 148, 151, 154, 157, 160, 163, 166,169, 172, 175, 178, 181, 184, 187, 190, 193, 196, 199, 202, 205, 208,211, 404, 452, 455, 467, 509, 539, 568, 650, 749, 1001, 1087, 1286,1637, 1823, 1835, 1841, 1889, 1898, 1901, 2111, 2225, 2252, 2279, 2309,2315, 2428, 2452, 2497, 2519, 3109, 3154, 3160, 3170, 3193, 3214, 3298,3331, 3346, 3388, 3397, 3404, 3416, 3466, 3491, 3500, 3572, 4181, 4411,4594, 4970, 5042, 5069, 5081, 5086, 5095, 5104, 5320, 5465, 5491, 6193,6541, 6778, 6853, 6928, 6934, 7030, 7198, 7351, 7712, 7826, 7922, 8194,8347, 8350, 8435, 8518, 8671, 8861, 8887, 9199, 9980, 10031, 10240,10519, 10537, 10573, 10589, 11078, 11278, 11324, 11489, 11642, 12034,12107, 12184, 12295, 12635, 12643, 12941, 12995, 13001, 13133, 13172,13246, 13514, 13522, 13939, 14362, 14720, 14926, 15338, 15524, 15565,15662, 15775, 16358, 16613, 16688, 16760, 17003, 17267, 17596, 17705,18157, 18272, 18715, 18994, 19249, 19348, 20221, 20855, 21400, 21412,21418, 21430, 21478, 21559, 21983, 21986, 22331, 22367, 22370, 22402,22447, 22535, 22567, 22571, 22660, 22780, 22802, 22844, 22888, 22907,23021, 23057, 23086, 23213, 23240, 23263, 23333, 23369, 23453, 23594,24143, 24176, 24319, 24325, 24565, 24587, 24641, 24965, 25067, 25094,25142, 25331, 25379, 25465, 25553, 25589, 25594, 25655, 25664, 25807,25823, 25873, 25925, 25948, 26002, 26008, 26102, 26138, 26141, 26377,26468, 26498, 26510, 26512, 26578, 26579, 26588, 26594, 26597, 26608,26627, 26642, 26767, 26776, 26800, 26876, 26882, 26900, 26917, 26927,26951, 26957, 26960, 26974, 26986, 27010, 27013, 27038, 27044, 27053,27059, 27061, 27074, 27076, 27083, 27086, 27092, 27094, 27098, 27103,27110, 27115, 27118, 27119, 27125, 27128, 27130, 27133, 27134, 27140,27143, 27145, 27146, 27148, 27149


15. The transmission apparatus of claim 9, wherein the preamblecomprises a P2 symbol that carries signaling information of a physicallayer in a DVB system.
 16. The transmission apparatus of claim 9,wherein the transmission unit further comprises a gradient unit thatadds the signal having the impulse characteristic to an informationsignal that is transmitted through data tones in the preamble, using agradient algorithm for PAPR reduction.
 17. A transmission apparatus forreducing a Peak to Average Power Ratio (PAPR) in a digital broadcastingsystem, comprising: a transmission unit for transmitting a frame inwhich a preamble is included; a memory for storing indexes of reservedtones used to transmit a signal having an impulse characteristic inlocations of sub-carriers that do not collide with a pilot signal of thepreamble; and a controller for generating the signal having the impulsecharacteristic according to the indexes of the reserved tones andcontrolling the transmission unit so as to transmit the signal havingthe impulse characteristic through the reserved tones in a symbol periodfor which the preamble is transmitted.
 18. The transmission apparatus ofclaim 17, wherein the digital broadcasting system uses OrthogonalFrequency Division Multiplexing (OFDM) as a transmission scheme, andlocations of the reserved tones vary according to a Fast FourierTransform (FFT) size.
 19. The transmission apparatus of claim 17,wherein when OFDM supports a plurality of FFT sizes, locations of thereserved tones are determined in accordance with the following table:FFT mode (Number of reserved tones) Indexes of reserved tones  8K (72)106, 109, 110, 112, 115, 118, 133, 142, 163, 184, 206, 247, 445, 461,503, 565, 602, 656, 766, 800, 922, 1094, 1108, 1199, 1258, 1726, 1793,1939, 2128, 2714, 3185, 3365, 3541, 3655, 3770, 3863, 4066, 4190, 4282,4565, 4628, 4727, 4882, 4885, 5143, 5192, 5210, 5257, 5261, 5459, 5651,5809, 5830, 5986, 6020, 6076, 6253, 6269, 6410, 6436, 6467, 6475, 6509,6556, 6611, 6674, 6685, 6689, 6691, 6695, 6698, 6701 16K (144) 104, 106,107, 109, 110, 112, 113, 115, 116, 118, 119, 121, 122, 125, 128, 131,134, 137, 140, 143, 161, 223, 230, 398, 482, 497, 733, 809, 850, 922,962, 1196, 1256, 1262, 1559, 1691, 1801, 1819, 1937, 2005, 2095, 2308,2383, 2408, 2425, 2428, 2479, 2579, 2893, 2902, 3086, 3554, 4085, 4127,4139, 4151, 4163, 4373, 4400, 4576, 4609, 4952, 4961, 5444, 5756, 5800,6094, 6208, 6658, 6673, 6799, 7208, 7682, 8101, 8135, 8230, 8692, 8788,8933, 9323, 9449, 9478, 9868, 10192, 10261, 10430, 10630, 10685, 10828,10915, 10930, 10942, 11053, 11185, 11324, 11369, 11468, 11507, 11542,11561, 11794, 11912, 11974, 11978, 12085, 12179, 12193, 12269, 12311,12758, 12767, 12866, 12938, 12962, 12971, 13099, 13102, 13105, 13120,13150, 13280, 13282, 13309, 13312, 13321, 13381, 13402, 13448, 13456,13462, 13463, 13466, 13478, 13492, 13495, 13498, 13501, 13502, 13504,13507, 13510, 13513, 13514, 13516 32K (288) 104, 106, 107, 109, 110,112, 113, 115, 118, 121, 124, 127, 130, 133, 136, 139, 142, 145, 148,151, 154, 157, 160, 163, 166, 169, 172, 175, 178, 181, 184, 187, 190,193, 196, 199, 202, 205, 208, 211, 404, 452, 455, 467, 509, 539, 568,650, 749, 1001, 1087, 1286, 1637, 1823, 1835, 1841, 1889, 1898, 1901,2111, 2225, 2252, 2279, 2309, 2315, 2428, 2452, 2497, 2519, 3109, 3154,3160, 3170, 3193, 3214, 3298, 3331, 3346, 3388, 3397, 3404, 3416, 3466,3491, 3500, 3572, 4181, 4411, 4594, 4970, 5042, 5069, 5081, 5086, 5095,5104, 5320, 5465, 5491, 6193, 6541, 6778, 6853, 6928, 6934, 7030, 7198,7351, 7712, 7826, 7922, 8194, 8347, 8350, 8435, 8518, 8671, 8861, 8887,9199, 9980, 10031, 10240, 10519, 10537, 10573, 10589, 11078, 11278,11324, 11489, 11642, 12034, 12107, 12184, 12295, 12635, 12643, 12941,12995, 13001, 13133, 13172, 13246, 13514, 13522, 13939, 14362, 14720,14926, 15338, 15524, 15565, 15662, 15775, 16358, 16613, 16688, 16760,17003, 17267, 17596, 17705, 18157, 18272, 18715, 18994, 19249, 19348,20221, 20855, 21400, 21412, 21418, 21430, 21478, 21559, 21983, 21986,22331, 22367, 22370, 22402, 22447, 22535, 22567, 22571, 22660, 22780,22802, 22844, 22888, 22907, 23021, 23057, 23086, 23213, 23240, 23263,23333, 23369, 23453, 23594, 24143, 24176, 24319, 24325, 24565, 24587,24641, 24965, 25067, 25094, 25142, 25331, 25379, 25465, 25553, 25589,25594, 25655, 25664, 25807, 25823, 25873, 25925, 25948, 26002, 26008,26102, 26138, 26141, 26377, 26468, 26498, 26510, 26512, 26578, 26579,26588, 26594, 26597, 26608, 26627, 26642, 26767, 26776, 26800, 26876,26882, 26900, 26917, 26927, 26951, 26957, 26960, 26974, 26986, 27010,27013, 27038, 27044, 27053, 27059, 27061, 27074, 27076, 27083, 27086,27092, 27094, 27098, 27103, 27110, 27115, 27118, 27119, 27125, 27128,27130, 27133, 27134, 27140, 27143, 27145, 27146, 27148, 27149


20. The transmission apparatus of claim 17, wherein the preamblecomprises a P2 symbol that carries signaling information of a physicallayer in a DVB system.